Polycarbonate has found many uses because, in general, it combines a high level of heat resistance and dimensional stability with good insulating and noncorrosive properties, and it is easily molded. It does, however, suffer from a tendency to craze and crack under the effects of contact with organic solvents such as gasoline. An undesirable result in polycarbonate which has crazed is that it is more likely to experience brittle rather than ductile failure. This disadvantage has been somewhat relieved by the practice of blending polycarbonate with various olefin polymers such as low density polyethylene or linear low density polyethylene, or thermoplastic rubbers such as ethylene/propylene copolymer. These added substances are capable of improving the resistance of polycarbonate to solvents, but they tend to delaminate and cause an offsetting reduction in the toughness, impact resistance and weldline strength of the blended polycarbonate composition. Such delamination, and the resulting loss of utility, is reported, for example, in U.S. Pat. No. 4,496,693.
Impact resistance in polycarbonate can be improved by the incorporation of emulsion or core-shell elastomers such as methacrylate/butadiene/styrene copolymer or a butyl acrylate rubber. However, these core-shell rubbers hinder processability of the blend by increasing viscosity and impart no improvement to the solvent resistance of polycarbonate. It would accordingly be desirable if modifers blended with polycarbonate for the purpose of improving its solvent resistance did not also deleteriously affect its toughness and impact and weldline strength, and cause delamination as evidenced by peeling or splintering in a molded article.